Test Description

WARNING: This page is about a different car, the 1995 Oldsmobile Ninety-Eight and 1995 Buick Park Avenue. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Test numbers refer to numbers on diagnostic chart.

Ensures EGR valve is allowing EGR flow and PCM is capable of controlling EGR valve.
Ensures control circuit is not shorted to ground.
Ensures control circuit is not open and that PCM quad-driver for circuit is properly functioning.

Fig 1: Code P0401 Schematic (3.8L) (EGR) Flow Test Failure

Fig 2: Code P0401 Diagnostic Flow Chart (3.8L) (EGR) Flow Test Failure